1. Field of the Invention
This invention relates generally to a hybrid powered vehicle that has an engine and an electric motor.
2. Description of Related Art
A hybrid powered vehicle is known which has both an engine and an electric motor and is selectively driven by the engine and/or the electric motor. Hybrid powered vehicles are roughly classified into series hybrid powered vehicles and parallel hybrid powered vehicles. The series hybrid powered vehicle uses an output of the engine for power generation only, and is driven exclusively by an output of the electric motor. On the other hand, the parallel hybrid powered vehicle can be driven by the output of the engine and/or the electric motor depending on the driving conditions. Thus, the parallel hybrid powered vehicle requires a drive system that is capable of transmitting the output of the engine and the electric-motor to an axle.
FIG. 6 schematically shows the structure of the drive system in the conventional parallel hybrid powered vehicle. As shown in FIG. 6, an electric motor 72 is arranged between an engine 70 and a transmission 80, and a rotor 73 of the electric motor 72 is axially and fixedly integrated with an output shaft 71 of the engine 70. Reference numeral 74 denotes a stator, which is fixed to a transmission case 81. Accordingly, the output of the engine and the electric motor is transmitted from the output shaft 71 of the engine 70 to an input shaft 82. Then, the output of the engine and the electric motor goes through a forward/backward rotation switching mechanism 83, and is converted by a continuously variable transmission mechanism 84. The output is finally transmitted to an axle.
In the above-mentioned conventional hybrid powered vehicle, the engine 70 and the electric motor 72 always rotate as one, and it is therefore impossible to use only the electric motor 72 as the drive source for the vehicle with the engine 70 being stopped. It is also impossible to regenerate energy solely by the electric motor 72 without running an engine brake during speed reduction.
To address this problem, it is necessary to provide a clutch mechanism between the engine 70 and the motor 72 so as to stop the transmission of the output between the engine 70 and the input shaft 82. This increases the full length, weight, cost and the like of the transmission 80.